<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style type="text/css">
        .list_con{
            width: 600px;
            margin: 50px auto 0;
        }
        .inputtxt{
            width: 540px;
            height: 30px;
            border: 1px solid #cccccc;
            padding: 0px;
            text-indent: 10px;
        }
        .inputbtn{
            width: 40px;
            height: 32px;
            padding: 0px;
            border: 1px solid #cccccc;
        }
        .list{
            margin: 0;
            padding: 0;
            list-style: none;
            margin-top: 20px;
        }
        .list li{
            height: 40px;
            line-height: 40px;
            border-bottom: 1px solid #cccccc;
        }
        .list li span{
            float: left;
        }
        .list a{
            float: right;
            text-decoration: none;
            margin: 0 10px;
        }
    </style>
    <script src="../js/jquery-1.12.4.min.js"></script>
    <script>
        $(function () {
            const $txt = $('#txt1');
            const $btn = $('#btn1');
            const $list = $('#list');

            $btn.click(function () {
                var sVal = $txt.val();

                // 判断输入框是否为空
                if (sVal === '') {
                    alert('请输入内容!');
                    return;
                }
                $txt.val('');

                var $li = $('<li><span>' + sVal + '</span><a href="javascript:;" class="up"> ↑ </a><a href="javascript:;" class="down"> ↓ </a><a href="javascript:;"  class="del">删除</a></li>');
                $li.appendTo($list);

                // var $del2 = $li.find('.del');

                // $del2.click(function () {
                //     $(this).parent().remove();
                // })
            });

            // var $del = $('.del');
            // $del.click(function () {
            //     $(this).parent().remove();
            // })

            // 上述过于复杂 下述较为简单
            $list.delegate('a', 'click', function () {
                // $(this).parent().remove();
                var sTr = $(this).prop('class');

                // 删除
                if (sTr === 'del') {
                    $(this).parent().remove();
                }
                // 上移
                if (sTr === 'up') {
                    // 判断是否是第一条
                    if ($(this).parent().prev().length === 0) {
                        alert('到顶了');
                    }
                    $(this).parent().insertBefore($(this).parent().prev());
                }
                // 下移
                if (sTr === 'down') {
                    // 判断是否是最后一条
                    if ($(this).parent().next().length === 0) {
                        alert('到底了');
                    }
                    $(this).parent().insertAfter($(this).parent().next());
                }

            })
        })
    </script>
</head>
<body>
    <div class="list_con">
        <h2>To do list</h2>
        <input type="text" name="" id="txt1" class="inputtxt">
        <input type="button" name="" value="增加" id="btn1" class="inputbtn">
        <ul id="list" class="list">
            <li><span>学习html</span><a href="javascript:" class="up"> ↑ </a><a href="javascript:" class="down"> ↓ </a><a href="javascript:"  class="del">删除</a></li>
            <li><span>学习css</span><a href="javascript:" class="up"> ↑ </a><a href="javascript:" class="down"> ↓ </a><a href="javascript:"  class="del">删除</a></li>
            <li><span>学习javascript</span><a href="javascript:" class="up"> ↑ </a><a href="javascript:" class="down"> ↓ </a><a href="javascript:"  class="del">删除</a></li>
        </ul>
</body>
</html>
